Change default direction of angle 0 in azimuthal integration

pyxem/tests/signals/test_diffraction2d.py

@@ -620,11 +620,11 @@ def test_internal_azimuthal_integration_data_range(self, corner, shape):
 
         assert np.allclose(np.nanmax(pol.data), max_val)
 
-    # polar unwrapping `arange` should look like [3 1 0 2]
+    # polar unwrapping `arange` should look like [1 0 2 3]
     # since data looks like:
     # 0 1
     # 2 3
-    # and the data gets unwrapped from the center and downwards, using the right hand rule
+    # and the data gets unwrapped from the center to the right
     @pytest.mark.parametrize(
         [
             "azimuthal_range",
@@ -633,19 +633,19 @@ def test_internal_azimuthal_integration_data_range(self, corner, shape):
         [
             [
                 (0 * np.pi / 2, 1 * np.pi / 2),
-                3,
+                1,
             ],
             [
                 (1 * np.pi / 2, 2 * np.pi / 2),
-                1,
+                0,
             ],
             [
                 (2 * np.pi / 2, 3 * np.pi / 2),
-                0,
+                2,
             ],
             [
                 (3 * np.pi / 2, 4 * np.pi / 2),
-                2,
+                3,
             ],
         ],
     )

pyxem/utils/calibration.py

@@ -409,6 +409,17 @@ def get_slices1d(self, npt, radial_range=None):
         return indexes, facts, factor_slices, radial_range
 
     def _get_slices_and_factors(self, npt, npt_azim, radial_range, azimuthal_range):
+        # In `_get_control_points`, positive x-direction is downwards, and positive y is to the right.
+        # This is 90 degrees off from the pyxem definition:
+        # https://pyxem.readthedocs.io/en/stable/tutorials/pyxem-demos/13%20Conventions.html
+        # As the azimuthal integration performed with a `Calibration`-object should align with
+        # the $X_L$ / $Y_L$-definitions in pyxem, we add pi/2 to the azimuthal range.
+        # This aligns the azimuthal angle 0 to $X_L$.
+        azimuthal_range = (
+            azimuthal_range[0] + np.pi / 2,
+            azimuthal_range[1] + np.pi / 2,
+        )
+
         # get the points which bound each azimuthal pixel
         control_points = _get_control_points(
             npt, npt_azim, radial_range, azimuthal_range, self.affine